Research On Key Technology Of Threshing And Cleaning Of Rape Combine Harvester On Sloping Land

Rapeseed is a major oil crop in China and the primary source of high-quality edible vegetable oil.However,due to outdated production methods and high production costs,the rapeseed production efficiency is relatively lower,which seriously affects farmers’ enthusiasm and constrains rapeseed industry development.China has a long history of rapeseed cultivation,extensive planting areas,and a wide variety of planting varieties.Due to complex terrain and geomorphic conditions conditions,the rapeseed mechanized production level is relatively low.In particular,mechanized harvesting of rapeseed on sloping fields is more difficult.The use of a universal harvester to harvest rapeseed can result in extremely high losses.This article focuses on the practicality issues of China’s rapeseed combine harvester in operating on sloping terrain,such as low processing capacity and cleaning rate.Based on the analysis of the structural characteristics and research frontiers of grain threshing and cleaning devices at home and abroad,combined with the planting system,variety characteristics,and biological characteristics of rapeseed in China,a new type of key component for cleaning rapeseed suitable on sloping land was designed.The method of combining theoretical analysis,computer simulation,bench testing and field trials was used to reveal the performance advantages of this new device.The specific research content includes:(1)Analysis and experiment of rapeseed plant biological characteristics.The main characteristics of rapeseed in China were analyzed,and a method for determining the rapeseed harvest period was developed.The main characteristics of excellent rapeseed suitable for mechanization were proposed.Through bench tests,the impact coefficient of restitution,static friction coefficient and rolling friction coefficient of the rape harvester’s ejecta were measured,and the value range of these coefficients was determined.The impact of different harvesting times on machine harvesting losses during the suitable harvest period was tested.The experimental results showed that with the passage of harvesting time,the overall yield of rapeseed showed a small decrease trend,with the loss caused by the rape pods peeling and bursting accounting for about 5% of the total loss.The harvest production in the afternoon was significantly lower than that in the morning,with an average decrease of 2.5%,which is due to a significant increase in cutting platform losses during the afternoon harvesting.(2)Design and research of new type threshing device.Single-factor bench tests were conducted to investigate the effects of different threshing components on threshing performance,threshing power consumption,and separation efficiency,and a semi-pinned-tooth and semi-ribbed rod threshing component was selected.A bidirectional drive threshing principle suitable for slope operation was proposed.By driving the concave screen to have a circumferential speed opposite to that of the threshing drum,reverse relative motion between the threshing drum and concave screen was formed to increase the threshing angle of grains.This increased the feeding and processing capacity of the harvester,reduced energy consumption,and improved the cleanliness of threshed grain without lengthening the threshing drum or increasing the equipment’s space occupation.A bidirectional drive threshing and separation device was designed,and a single-factor test was conducted to investigate the factors affecting the separation performance.The experimental results showed that the stem moisture content,drum speed,concave screen speed,baffle angle,and grain straw ratio all had significant effects on the threshing loss rate,impurity rate,and threshing power consumption.A comparative experiment was conducted to investigate the effects of the traditional fixed concave threshing device and the bidirectional drive threshing device on threshing loss rate,breakage rate,and threshing power consumption under different slope conditions.The results showed that the traditional fixed concave threshing device had significant changes in threshing performance with slope variation,while the bidirectional drive threshing device had a smaller effect,indicating that the bidirectional drive threshing device can adapt to slope operations.(3)Research on key technology of sloping land rape combine harvester clearing.In response to the problem of high cleaning losses caused by material accumulation on one side due to the of the machine body tilting during slope operation of the oilseed combine harvester,a self-balancing cleaning screen device that can adapt to gentle slopes of up to 10° and a control system based on a fuzzy PID control algorithm were developed.In order to verify the performance of the fuzzy PID algorithm applied to this system,simulation tests,system response tests and laboratory test were carried out.The experimental results showed that the system had good tracking performance when the inclination amplitude did not exceed 10°,with a maximum leveling error of 0.62°,a maximum leveling time of1.85 s,and a maximum overshoot of 1.5°,meeting field operation requirements.Field test results showed that the automatic leveling system had good tracking performance under continuously changing body tilt angles of the harvester.When the inclination angle of the harvester body was within the range of 10°,the system could stably perform real-time leveling of the cleaning screen.As the inclination angle of the harvester increased,the cleaning losses of the harvester equipped with the automatic leveling system could still be maintained at a relatively low level.The cleaning loss rate of the leveled harvester was only 1.2% higher than the error rate of flat field operation,which met the accuracy requirements of the system design.(4)Simulation study on the bidirectional driving threshing and separating device based on DEM(discrete element method).Based on the basic theory of DEM and the characteristics of rapeseed elastoplastic biomaterials,The oilseed rape was simplified as a soft sphere model,and the contact force between particles was simplified.To improve simulation efficiency and reduce model error,the discrete element model of oilseed rape plants was simplified as consisting of stem and silique,ignoring the effect of silique on the threshing process.By using the discrete element model of oilseed rape plants,the effects of the angle of the guide plate and the speed of the concave plate on the grain motion characteristics were studied.The material distribution under different tilt angles and speeds of the rotating concave plate and the fixed concave plate was analyzed.The simulation results showed that the material of the fixed concave plate was mainly concentrated in the front,while the longitudinal material distribution of the rotating concave plate was flatter than that of the fixed concave plate.It was concluded that for the rotating concave plate,the length of the drum needs to be increased to further improve the material separation ability.(5)Optimization design and experimental research on bidirectional-driven threshing device.By means of orthogonal experiments,the influence laws of threshing cylinder speed,concave screen speed,and threshing clearance on threshing performance were studied,and the significance degree of these parameters on seed damage rate and grain cleaning rate was determined.Regression model was established to optimize and determine the best working parameters,and field performance tests were conducted based on the experimental results to verify the feasibility and operational performance advantages of the threshing device under actual operating conditions.The orthogonal experiment showed that when the threshing cylinder speed was 782.4r/min,the concave screen speed was 89.2r/min,and the guide plate angle was 40°,the threshing loss rate and seed damage rate were 4.02% and0.87%,respectively.The on-site verification test showed that the threshing loss rate and seed damage rate of optimized bidirectional-driven threshing device were 4.25% and 0.93%,respectively.Compared with the threshing loss rate and grain damage rate of fixed concave screen,the threshing loss rate and grain damage rate of optimized bidirectional-driven threshing device were reduced by 2.17% and 1.65%,respectively.